-LRB- CNN -RRB- -- Twelve photographers from four continents have been shortlisted for the fourth Prix Pictet award in photography and sustainability .

This year 's theme of `` Power , '' has `` enormous breadth , embracing contradiction and paradox in equal measure that has uncovered images and issues that are both awe-inspiring and disturbing , '' organizers say .

The aim of the award is to use the power of photography to raise public awareness of the social and environmental challenges of the new millennium .

The winner will be announced by Kofi Annan , the awards ' honorary president , in October at the opening of the finalists ' exhibition of the shortlisted works at the Saatchi Gallery in London . The exhibition runs from the 10th to the 28th of October 2012 .

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Annual Prix Pictet photography prize announces shortlist

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Competition designed to raise awareness of social and environmental challenges

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Twelve photographers nominated ; Winner will be announced by Kofi Annan in October